1. Field of the invention
The present invention relates to an office machine keyboard comprising a layer of elastic material formed with an array of individually depressable areas constituting the keys of the keyboard.
2. Description of the prior art
The keyboards formed by elastic material solve the problems concerned, for example, the infiltration of foreign bodies into the interior of the keyboard itself, the insulation of the fingering area from any possible internal electrical apparatus and the partial absorption of the noise typical of office machines.
The layer of elastic material is generally mounted on a rigid supporting surface provided with holes permitting the passage of rigid shanks connecting each key with the encoding device located below the supporting surface.
A very importantl problem arising in keyboards formed by a layer of elastic material is the designation of the characters. One solution to this problem provides for the formation of shaped recesses in the fingering surfaces of the layer of elastic material; by filling the recesses with another material of different colour the characters are obtained.
This solution and other similar solutions are very complex in manufacture and, moreover, good adhesion between the two materials in the course of time is not certain, so that the character tends to disappear, with poor aesthetic results.
Another known solution consists in the arrangement of inserts of disc form which have the character printed on a plane surface, between a layer of rubber and an overlying layer of transparent elastic material, the whole resting on a supporting lattice of rigid material. This solution also presents problems connected with the complexity of the process and, moreover, the character must be of a colour different from the colour of the insert so that it may be visible.